Std bump

Stream: mathlib4

[Scott Morrison]

#8700 is now the candidate for bumping Mathlib to the latest Std.

If anyone available to help get it over the line? Pinging @Eric Wieser and @Alex Keizer, as they've been looking at it. Hopefully it is just a matter of addressing Eric's comments.

I'm about to go release v4.3.0 and then v4.4.0-rc1, and so this PR will soon be blocking upgrading Mathlib.

[Eric Wieser]

I think there are some easy CI issues to resolve as well